Sidewall Dominated Characteristics on Fin-Gate AlGaN/GaN MOS-Channel-HEMTs

The fin-gate structure was fabricated onto AlGaN/GaN MOS channel-high electron mobility transistors (MOSC-HEMTs), and the fin sidewall contribution to the MOS channel characteristics was investigated. In fin-gate MOSC-HEMTs (Fin-MOSC-HEMTs) with 120-nm fin width, significant suppression of short channel effect is obtained, but the threshold voltage (Vth) becomes lower than that of conventional MOSC-HEMTs. The fin width dependence shows continuous Vth decrease by decreasing the fin width, indicating that the narrower fin-gate channel is dominated by the fin sidewalls that are depletion mode nature. The channel sheet resistance extracted from channel length dependence and device transconductance for Fin-MOSC-HEMTs are superior to those of conventional MOSC-HEMTs when they are normalized by effective gate width as the summation of fin width, indicating contribution from sidewalls to channel conduction. Temperature dependence of Vth shows clearly different behavior between the MOSC-HEMT and Fin-MOSC-HEMT. These results demonstrate sidewall-dominated characteristics of these Fin-MOSC-HEMTs.